Method for determining processability of tar sand



United States Patent Ofiice 3,273,957 Patented Sept. 20, 1966 3,273,967 METHOD FOR DETERMINING PROCESSABIHTY (BF TAR SAND Omer L. Wilson, Tulsa, Okla., assignor to Cities Service Research and Development Company, a corporation of Delaware No Drawing. Filed May 7, 1963, Ser. No. 278,751 8 Claims. (Cl. 23-230) This invention relates to geochemical exploration and relates more particularly to a method for determining the ease with which bitumen can be separated from tar sand and the selective mining of tar sand.

In various localities throughout the world, deposits of bituminous sand are found in which the oil or tarry matter has a density greater than 1.0. The most extensive and best-known deposits of this type occur in the Province of Alberta in the Athabasca district. These Alberta tar sands extend for many miles and occur in thicknesses varying up to more than 200 feet, and probably consti' tute the largest presently known petroleum deposit of any type. Typically, the composition of these sands contain, by weight, from about 6% to about of oil (or bitumen); from about 1% to about 11% of water; and from about 70% to about 90% of inorganic solids. However, tar sand containing larger or smaller quantities of these ingredients is not unusual. The major portion, by weight, of the inorganic solids is fine grain quartz sand having a particle size greater than about 0.1 millimeter and less than about 1.0 millimeter. The remaining inorganic solid matter has a particle size of less than 0.1 millimeter and is referred to as fines. The fines contain clay and silt including some very small particles of sand. The fines content typically vary from about 10% to about by weight of the solid inorganic content of bituminous sand.

The phrases tar sand or bituminous sand are used to refer generally to all granular solid materials soaked with liquid or semiliquid hydrocarbonaceous material although they specifically refer to a characteristic type of bituminous solid consisting of discrete particles of sand bound together by a continuous heavy hydrocarbon oil phase.

The oil obtained from these sands is a viscous, tarry material and in its crude state does not command a high price; hence, any method suitable for recovering it must involve a minimum expense to be attractive for commercial practice. Various methods are known for extracting the oil from bituminous sand. Generally the oil is separated from the tar sand by extraction such as with a hydrocarbon solvent, or the formation of an emulsion with water or combinations of these procedures with or without the use of various chemicals to facilitate recovery of the bitumen. These techniques can be further implemented with various separation techniques such as centrifuging or settling. The two best known methods for recovering bitumen from tar sand are known as the hot water method and the cold water method. In the former the tar sand is jettisoned with steam and mauled with a small proportion of water at about 176 F. and the pulp is then dropped into a turbid stream of circulating water and carried to a separation cell maintained at about 185 P. where the oil rises to the top as a froth from which it is drawn oil.

The so-called cold water method does not involve heating the tar sand other than whatever heating might be required to conduct the operation at a temperature of about 73 to 81 F. This process involves milling a mixture of the tar sand, kerosene, water and soda ash and then settling at a temperature within the specified range. A mixture of oil and kerosene floats to the top of the settling zone and is removed. In addition to the hot or cold water methods various methods are known, which again depend on extracting the bitumen from the tar sand, whereby the process is practiced in situ. It is apparent, however, that the separation of the oil from the tar sand is not a very easy matter and the success of an operation for recovering such oils will depend on the ease with which the oil can be separated.

Various techniques are employed in the mining of the tar sand. For instance, mining on the surface or nearsurface deposits of tar sand can be performed by the usual procedures to produce a raw tar sand material consisting of chunks or pieces of tar sand not exceeding about twelve inches in average dimensions. This may be done by open-pit mining in which the over-burden is stripped away and the tar sand is mined by means of bulldozers, clam-shell shovels, and similar equipment. Drilling and blasting may also assist in the breaking up of the tar sand into the afore-mentioned sized particles. The mined material is then transferred to processing for separation of the oil which as described above can be accomplished by various means.

Extensive tests have shown that the tar sand and particularly Athabasca tar sand vary greatly in their processability, that is, the ease with which the bitumen is separated from the tar sand. Some sands process easily while others tenaciously hold on to the oil. Thus, when employing the hot water process recoveries of oil can range from about 50% to upwards of The processability of the tar sand varies greatly even within a fairly localized area such as within an acre or two within an exploration zone. Although the quantity of oil may be the same throughout the entire zone the ease with which the oil can be separated from the tar sand differs. Also areas which are separated by as little as one hundred or two hundred yards show different processability characteristics. Up to the time of the present invention, it is not believed that there was any known method for determining whether a sample of bituminous sand would process easily or not. It can be seen that a simple and convenient method whereby a sample of tar sand can be taken and subjected to analysis to determine its processability is of great value.

It has now been found that the ease with which the oil can be separated from tar sand is dependent on the amount of iron in the tar sand. There is a correlation between iron and processability of the tar sand with the higher iron content being indicative of the more easily processable tar sand. Thus, by employing the same processing method higher recoveries are obtained from sands which contain larger quantities of iron but the same quantity of oil.

This invention can be employed for geochemical prospecting. In geochemical prospecting, tar sand samples are taken at spaced distances over the prospect area. The samples may be taken along a traverse or a plurality of traverses or otherwise over the prospect area in accordance with usual procedures in the art for determining bitumen content. The tar sand samples can then be analyzed for iron content and the iron content of the samples is correlated with the sampling locations to determine the areas having the more easily processable tar sand.

This invention can also be employed for determining the relative ease or ditliculty of the separation of the oil from tar sand in a particular area, in determining the percentage of oil to be recovered by fixed processing conditions, or for correlating the severity of processing conditions required for percentage recovery of oil from the tar sand with the amount of iron the tar sand contains. Thus, samples of tar sand from one locality having a lower iron content than from another locality will require more severe processing conditions such as higher temperatures, greater or more severe agitation, larger quantities of chemicals, e.g. alkaline materials or surfactants or the use of secondary recovery equipment in order to obtain the same percent recovery of oil, based on the weight of total oil present in the tar sand, as compared to tar sand having a greater iron content.

Although applicant does not wish to be bound by any theory, it is believed that the bituminous cells in tar are charged positively due to nitrogen compounds present. The clay and colloidal quartz grains are negatively charged. Thus the clays and colloidal quartz are attracted to the bituminous cells due to the opposite charges. However, in the presence of iron and particularly water-soluble iron salts or iron compounds soluble in the tar sands, the iron ions are positively charged and they form a positively charged barrier around the quartz and clay materials. Hence, the clay and quartz crystals assume an effective positive charge and since they now have the same charge as the bituminous cells, the two are repelled. In this manner it is believed that the presence of iron causes the tar sand to be easier to process.

When the process of this invention is used for determining processability of tar sand it is preferred to mine those sands which have an iron content which correlates with at least a 75% recovery of its oil, by weight, and particularly at least an 80% or 85 recovery by the process employed. It can be seen that the invention is particularly applicable for processes which show a wide variance in their efficiency for removing the oil, such as the methods described herein-above in which a variance of 50% to about 96% is not uncommon, or when the percent recovery of oil, based on total oil content in the tar sand, varies by more than about and preferably over for different samples of tar sand with the particular method employed. Selective processing, particularly in the Athabasca district can be practiced by processing tar sand from areas whose iron analyses show that they contain greater than about one-sixth the quantity of iron of the numerical average of the iron content in the samples from the exploration zone, while rejecting and not processing tar sand containing less than about one-sixth the quantity of iron as the numerical average.

In addition to iron, it has been found that zinc, calcium, potassium, nickel, vanadium, are found in tar sand. However, zinc and iron and particularly iron are the only elements which appear to vary to any extent so as to give an indication of processability. Therefore this invention also applies to zinc content, and particularly water soluble zinc salts in the tar sand in the same manner as described for iron.

In determining the relative quantity of iron in the tar sand it is sufficient if an elemental analysis is performed which would include all types of iron available although it is preferred the measurements be made on watersoluble iron in the tar sand. A suitable method for determining water-soluble iron salts is by intimately admixing a sample of the tar sand with about 2 or 3 times its volume of kerosene, centrifuging the mixture, decanting the kerosene and kerosene soluble fraction and making an iron analysis on the residue. The size of the sample of tar sand analyzed can vary, dependent on the analytical technique employed to determine iron content. The analyses can be performed by various means such as by the use of an X-ray spectrograph, wet chemical methods, emission spectroscopy and the like.

The above analyses need not be quantitative since the ease of processability of the various tar sand samples is relative.

The following example is illustrative of the invention.

Example 1 In an exploration area of about half of a square mile five holes were made about 1,000 feet from each other into the earth below the surface. A sample from each hole was obtained. A fifty cc. portion of the sample was then analyzed for iron by separating the bitumin from the tar sand with kerosene in a centrifuge, after thorough agitation, and then making an X-ray spectrographic analysis of the relative iron contents in the kerosene insoluble portion of the tar sand. The localities from which the samples were taken were designated as areas: A, B, C, D, and E. The exact quantity of iron contained in the kerosene insoluble portion of the tar sand was not known since only relative quantities of iron were obtained. However, in the analysis 1.0 part of iron represents half as much iron as 2 parts of iron and 4.4 parts of iron represents about 11 times more iron than 0.4 part of iron in the following table. The tar sand from each of the areas was treated substantially by the cold water method and the percent of recovery from the different areas was determined. The results of these analyses and the percent oil recovery, based on the total quantity of oil present in each sample are shown in Table 1.

the iron content the greater the percent recovery of oil from the tar sand.

The process of this invention is particularly applicable for determining iron content of tar sand which contains from about 6 to about 10% oil. Tar sand containing less than 6% oil is uneconomical to process due to the low oil content irrespective of the portion of oil that can be recovered. Tar sand having an oil content above 10%, even though it may be difficult to process, can still generally yield sufi icient oil to be economically feasible. However, tar sand containing between about 6 to 10% of oil is on the borderline with the tar sand having relatively easy processability e.g. processability which yields greater than about recovery by the method employed, being desirable for processing whereas that giving less than about 85% recovery of its oil content being undesirable for processing. The process of this invention permits the operator to selectively mine tar sand having an oil content of 6% to about 10% wherein the more easily processable tar sand is mined.

In addition to iron or zinc varying from locality to locality in an exploration zone, the iron or zinc content can also vary at different depths within one locality. Generally, the tar sand extends from about 50 to 200 feet below the surface. In accordance with this invention, samples of tar sand can be obtained at different levels of an exploration zone, such as one varying from about 0.1 to about 2 square miles, in order to determine the depths for mining the more easily processable tar sand. Of course, this method will also determine the areas within the exploration zone which have poorly processable tar sand. The analyses, of course, are correlated with the sample locations and the more easily processable tar sand, as to depth and area, within the exploration zone can be charted and finally mined and processed.

Having thus described my invention, it will be understood that such description has been given by way of illustration and example only and not by way of limitation.

What is claimed is:

1. A method for determining the processability of tar sand which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of samples for their content of a member selected from the group consisting of iron and zinc, and correlating the analyses with the sample locations in said exploration zone to determine the location having the higher content of said member and hence the more easily processable tar sand.

2. A method for determining the processability of tar sand in which the processability is determined as a function of Water soluble iron content, which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of said samples for water soluble iron content, and correlating the analyses with the sample locations in said exploration zone to determine the area having the higher Water soluble iron content and hence the more easily processable tar sand.

3. A method for determining the processablity of tar sand in which the processability is determined as a function of iron content which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of samples for iron content, said analysis being performed on the tar-free residue of the tar sand to determine the relative quantity of iron in said samples, and correlating the analyses with the sample locations in said exploration zone to determine the area having the higher iron content and hence the more easily processable tar sand.

4. A method for selectively mining tar sand which comprises collecting samples of tar sand, analyzing a plurality of said samples for their content of a member selected from the group consisting of iron and zinc, correlating the analysis with the sample locations to determine the areas having the higher content of said member and mining tar sand from those areas having the higher iron content.

5. A method for selectively mining tar sand and limiting the areas mined to those in which the oil is more easily removed from the tar sand which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of samples from said zone for iron content, correlating the analyses with the sample locations in said exploration zone to determine the area having the higher iron content and the more easily processable tar sand and mining tar sand from those areas having the higher relative iron content while bypassing those areas having a lower relative iron content.

6. A method for selectively mining tar sand having an oil content of from about 6% to about 10% which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of said samples having a total oil content of from about 6% to about 10% for watersoluble iron content, then correlating the analysis with the sample locations to determine the area of said exploration zone having the higher iron content and subsequently mining tar sand in those areas having the higher iron content while substantially by-passing those areas having the lower iron content.

7. A method for determining the processability of tar sand which comprises collecting samples of tar sand at diitcrent depths within an exploration zone, analyzing a plurality of said samples for their content of a member selected from the group consisting of iron and zinc and correlating the analyses with the individual depths in said zone to determine those with the higher iron content, charting the location as to both depth and area having the higher iron content and selectively mining the charted area within the exploration zone.

8. A method for selectively charging tar sand yielding an oil recovery of at least by weight of the oil in the tar sand, in an extraction recovery process having yields which vary by over 20% for different tar sand samples and capable of recoveries of at least 80% dependent on the tar sand sample, which comprises collecting samples of tar sand from an exploration zone, analyzing a plurality of samples from said zone for water soluble iron content, correlating the analyses with the sample locations in said exploration zone, correlating the analysis with the quantity of water soluble iron in tar sand necessary for obtaining an oil recovery of at least 80%, by weight of the oil in the tar sand by the said process employed for extracting the oil from tar sand, and charging to said oil recovery process tar sand from the exploration zone locations having the quantity of iron correlating with at least an 80% recovery of the oil.

References Cited by the Examiner UNITED STATES PATENTS 2,278,929 4/1942 Horvitz 23230 2,336,612 12/1943 Horvitz 23230 OTHER REFERENCES Pasternack, David S., Petroleum Substitutes From Tar Sands, Chemical Engineering Progress (vol. 56, N0. 4), April 1960, p. 72.

MORRIS O. WOLK, Primary Examiner.

H. A. BIRENBAUM, Assistant Examiner. 

1. A METHOD FOR DETERMINING THE PROCESSABILITY OF TAR SAND WHICH COMPRISES COLLECTING SAMPLES OF TAR SAND FROM AN EXPLORATION ZONE, ANALYZING A PLURALITY OF SAMPLES FOR THEIR CONTENT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF IRON AND ZINC, AND CORRELATING THE ANALYSES WITH THE SAMPLE LOCATIONS IN SAID EXPLORATION ZONE TO DETERMINE THE LOCATION HAVING THE HIGHER CONTENT OF SAID MEMBER AND HENCE THE MORE EASILY PROCESSABLE TAR SAND. 